1. Field of the Invention
The present invention relates to an apparatus for injection of powder into a metal melt, comprising a charging container for powder (powder sender) and an injection apparatus, such as a lance, and more particularly to such apparatus in which the powder is sieved prior to injection in the melt.
2. Prior Art
U.S. patent application Ser. No. 970,803, filed Dec. 18, 1978, now U.S. Pat. No. 4,244,562 discloses an injection apparatus of the type specified herein, and the present application is an improvement of the apparatus according to the older application.
In the apparatus according to the older application there is obtained a solution to the problem of achieving an even, pulse-free and safe supply of powder, alloying additives, refining agents, charge powder and/or reducing agents to a metallurgical melt. Also environmental problems in the form of dust and clogging, which were obtained earlier, have been solved. The invention according to the older application is characterised in that a lance and a charging container are interconnected to form one unit, which is raisable and lowerable relative to the melt (which is to be further charged, supplied with alloying additives, refined, decarburized and/or reduced). Despite long transportation paths to the melt, it is possible to obtain an even, efficient, and easily controllable injection, for example through the roof of a channel-type injection furnace.
A problem with this form of injection, however, is the achievement of a proper, desired grain size for the powder to be injected, as it is desirable to avoid supplying, for example, coarse powder, which for example, may cause clogging of supply conduits or cause undesirable results in the metallic melt. It is also desirable to achieve an even supply and not, for example, pulsating charging of the melt. In other words, it is desirable to achieve as disturbance-free an injection as possible, and the means according to the present invention provides a solution to the problems mentioned as well as other associated problems.